The present invention relates to a vehicle lamp, and more particularly, to prevention of surface sinkage during cooling at a time of formation of a vehicle lamp lens and to improvement in external appearance of a vehicle lamp lens.
Discussion of the Related Art
A widely used vehicle lamp has a reflection portion including recursive reflection elements formed as a part of a lens to cover an opening of a lamp body. Such a vehicle lamp is widely used, for example, as a rear combination lamp of a car, or the like.
FIGS. 6 and 7 show an example of a conventional vehicle lamp. The vehicle lamp 100 includes a vessel-shaped lamp body 101, a lens 103 covering an opening 102 of a lamp body 101, and a reflector 106 in a lamp chamber 104. The lamp chamber 104 is defined by the lamp body 101 and the lens 103. The reflector 106 reflects light from light sources 105a, 105b, and includes left and right reflecting portions 107a, 107b. The left and right reflecting portions 107a, 107b are connected to each other through a connection portion 108.
The lens 103 is shaped as an outwardly-convex gently curved surface. A reflection portion 110 includes a large number of recursive reflection elements 109 and is formed in an inner surface of the lens 103 at a portion corresponding to the connection portion 108. A circumferential wall-like attachment rib 111 projects from an outer circumference of the reflection portion 110. A flat plate-like sealing plate 112 is attached to the attachment rib 111 by ultrasonic welding. The sealing plate 112 prevents a reduction in effectiveness of the recursive reflection elements 109 by preventing entry and deposition of water and dust.
A forward end surface 113 of the attachment rib 111 must be located in the same plane. The forward end surface 113 is an attachment surface to which the sealing plate 112 must be attached, and the attachment surface is pressed through the flat plane-like sealing plate 112 by a flat end surface of a vibration portion (ultrasonic welding horn) of an ultrasonic welding apparatus at the time of welding.
Further, the conventional vehicle lamp 100 is configured so that the amount of projection of the attachment rib 111 is changed to partially correspond to the curvature of the lens 103 so that the attachment surface 113 is located in the same plane. That is, as shown in FIG. 7, the attachment rib 111 is formed so that the amount of projection of the attachment rib 111 increases approaching the laterally central portion, and decreases approaching each of the laterally opposite end portions from the laterally central portion.
If the amount of projection of the attachment rib 111 in the laterally central portion is larger than that in the other portion, the base end portion of the attachment rib 111 must be thicker than the forward end portion of the attachment rib 111. This allows the thickness of the attachment surface 113 to be made even over its entire circumference, because it is necessary to provide a release angle in the mold-releasing direction at the time of molding. Accordingly, only the laterally central portion of the lens 103 in the portion corresponding to the attachment rib 111 appears expanded in a vertical dimension (see FIG. 8) when the lens 103 is observed from the outside. Therefore, appearance of the vehicle lamp is poor.
Further, particularly in the laterally central portion, there arises a problem when so-called surface sinkage is easily generated in outer portions 114a, 114b (see FIG. 9) of the lens 103 (corresponding to the attachment rib 111). This occurs during cooling at the time of formation of the lens 103 because the base end portion is thick and the amount of projection of the base end portion of the attachment rib 111 from the inner surface of the lens 103 is large, so that the mass increases.